The present invention relates to a method for continuous thermal treatment of a textile product web, in particular for dye fixing, as well as to an arrangement for performing the inventive method.
During coloring it is necessary to fix a dye applied on the textile product web. The dye fixing can be performed by retaining the product web with applied dye solution at room temperature or the moist or dried product web at higher temperatures. The fixing treatment depends on the material of the product web and the applied dye.
During coloring of chemical fibers with dispersion dyes, for example it is known to first dry the product web with applied dying solution and subsequently to fix the dye at higher temperatures on the product web.
German patent document DE/A 16 35 140 discloses a method of continuous dye fixing of chemical fibers in product webs by a high temperature treatment with convective heat transfer, for example from nozzle-aerated fixing tension frames. For blending of the fixing effect first a fast heating and subsequently a tension treatment is performed. During the fast heating the product web is guided in tensioning chains and during the retention treatment over normal guiding rollers.
During coloring of cotton or cellulose with reactive dyes it is for example known to first dry the product web with the dye solution applied to it and subsequently to let the dye react at higher temperatures with the fibers of the product web. For this first purpose a promoter, such as urea, is required, which is mixed to the dye solution. The promoter holds the dye in solution during drying and evaporates during fixing. As a treatment gas, heated air is used. The use of an aggressive promoter, such as urea, can be reduced or avoided by treatment of the product web with applied dye solution with a steam-air mixture.
From the patent document EP/A 0 864 683 it is known to impregnate a product web of cellulose knit or woven fabric with an aqueous dye solution of a fiber-reactive dye at a temperature of 20-25xc2x0 C. to compress it, and to fix it without intermediate drying in an unsaturated water steam-air mixture, with 10-80 vol. percent of water steam, at a temperature of 100-160xc2x0 C. and with an adjustable wet temperature of the moist product between 50 and 95xc2x0 C. The product is guided with a speed, which is regulated by the measured residual moisture of the product after exit from the fixing device. The residual moisture amounts to 10-25 weight percent with respect to the product weight.
The patent document WO 97/14839 discloses a corresponding method and a device for dye fixing of cellulose products with reactive dyes, in which an optimal dye yield is obtainable without aggressive promoter quantities. In a padder the dying solution is applied on the product, and is subsequently guided in a chamber of an air dryer. In this chamber a steam contact is maintained in the order of 25 vol. percent of air and is supplied so that the product of the outlet of the chamber has a reaction-ready residual moisture. For this purpose two regulating circuits are used, namely one for the steam content and another for the residual moisture of the product web. In other words during this process expensive measuring and regulating devices are needed. This fixing method requires, due to the retention time of the order of two minutes in a continuous process with a product web speed of for example 40 m/min, a product extent in the retention aggregate, here a hot flue, of at least 80 m. It is therefore not efficiently usable for small quantities to be colored (small meter lengths).
Accordingly, it is an object of present invention to provide a method of continuous thermal treatment, in particular for dye fixing, in which the treatment gas contains hot steam and which can be used efficiently for smaller meter length.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a method of continuous thermal treatment of a textile product web for dye fixing, comprising the steps of applying a dye solution to a product web; transporting the resulting moist product web with the dye solution applied to it through at least one treatment chamber; bringing the moist product web with the applied dye solution in contact with a treatment gas in the treatment chamber. The treatment gas contains hot steam, i.e. overheated water steam.
It is another object of present invention to provide an arrangement with which the new method of thermal treatment can be performed efficiently and faster.
In keeping with these objects, another feature of the present invention resides, briefly stated, in an arrangement for continuous thermal treatment of a textile product web for dye fixing, comprising a steam-tight housing with at least one treatment chamber having at least one circulating device with at least one circulating fan, nozzle boxes arranged above and below the product web; a transporting device for substantially flat guidance of the product web through the housing, the transporting device including at least one roller conveyor arranged at a distance from a front wall of the housing.
In the inventive method for continuous thermal treatment of a textile product web, the moist product web provided with dye solution is transported through at least one treatment chamber and is brought into contact in the treatment chamber with a treatment gas, which is composed of hot steam. The treatment gas is at least 80 vol. percent, preferably 95-120 vol. percent, or, in other words, approximately pure hot steam. The temperature of the hot steam amounts to 105-230xc2x0 C. The hot steam used in the method according to the invention is overheated water steam substantially at atmospheric pressure.
With a higher steam content, higher temperatures of the product web are reachable during the thermal treatment. In particular with pure hot steam the product web temperature is increased to substantially 100xc2x0 C. The higher treatment temperature accelerates the reaction of the dye with the fibers during fixing of reactive dye on cotton or cellulose. This leads to lower fixing times, correspondingly lower retention times in a treatment device, and possibly smaller devices.
A higher steam content of the treatment gas accelerates, due to the condensation ability of the hot steam, the heating, which leads to a further reduction of the required retention time. In a surprising manner the inventive treatment method, despite the higher steam content and the higher product temperature, and thereby increased drying, leads to good fixing results. In other words, it leads to a good dye yield and a good coloring quality, which correspond to the results of the prior art.
The drying of the moist product web during the treatment with hot steam provides lower fixing times for complete fixing. This is achieved by an acceleration of the fixing process, i.e. the reaction of the reactive dye with natural fibers, such as cotton and cellulose, by the drying.
The input moisture of the product web provided with the dye solution of the reactive dye amounts to 40-80%. For many reactive dyes the use of urea can be dispensed with.
The temperature of the hot steam can be preferably 160-230xc2x0 C. The higher temperature of the treatment gas and thereby the higher the temperature difference between the treatment gas and the product, the greater the heat transfer and thereby faster the heating time of the product web and the drying of the product web.
The retention time of the product web in the arrangement is 50-60 seconds, preferably 10-30 seconds. This time is sufficient for complete fixing for good dye yield and makes possible to have an arrangement with a smaller structural dimension.
In a surprising manner it has been determined that with the inventive method optimal fixing results are provided with a residual moisture of the product web smaller or equal to the equilibrium moisture under normal conditions, or in other words approximately 10% moisture to the weight of the product for cellulose and approximately 8% moisture for cotton. This can be explained by the above mentioned accelerated action of the drying for the dye fixing. Regulation of the residual moisture of the product web in the arrangement is not needed.
In principle all processes, with which the product web can be brought in contact with hot steam, can be used for the inventive method.
For this method, a guidance of the product web through the chamber filled with hot steam can be performed in form of suspending loop or a meandering guidance of the product web in two rows of guiding or transporting rollers, as far as it is suitable for transportation of a moist, colored and unfixed product web.
For improving the heat transfer from hot steam to the product web and thereby reducing the retention time, the product web in accordance with the present invention can be brought into contact with hot steam which is guided in a circulating process, through nozzles which are oriented toward the product web. This is possible in the inventive method without dye running, since because of the high steam content and in some cases the high steam temperature, a fast drying of the product web and thereby of the dye is provided.
Devices with a meandering guidance of the product web around two rows of rollers or on nozzles oriented toward the product web are known as hot flu. The above mentioned devices have however as disclosed in the patent document WO 97/148 39 a very high product extent and are, for example due to untightness, not suitable for an operation with hot steam.
A further improvement of the heat transfer can be obtained when the product web is transported substantially flat through the treatment chamber and is brought in contact with hot steam from nozzle boxes arranged above and below the product web.
Devices, by which the product web is transported flat and brought in contact with a treatment gas by nozzle boxes, namely nozzle-equipped fixed tension frames, are known for fast heating during dye fixing of chemical fibers, such as thermal insulation, for example from the German patent document DE/A 16 35 140.
Devices of this type, in which hot steam can be suitably used as treatment gas are disclosed in the German patent document DE 35 11 95. In particular a suspension dryer and a tension frame dryer.
During a suspended guidance of the product web in a suspension dryer the danger of producing wavy portions of the product web which can lead during fixing to dye running is high. Tension chains during dye fixing have the disadvantage that the edge markings are caused.
A further, corresponding device, namely a tension frame dryer usable for hot steam treatment is disclosed in the German patent document DE 195 46 344. The inlet slot and the outlet slot of this dryer are arranged in a bottom of its housing. The product web is guided through the dryer from the inlet region to the outlet region flatly and therefore horizontally.
Preferably the product web in the inventive method is transported by means of a roller conveyor arranged at a distance to a front wall of the housing with a longitudinal tension, in particular of 10-100 N/M through the treatment chambers. The distance from the front wall amounts to at least 20% preferably 30% of the length of the horizontal transporting path of the product web through the treatment chambers. The product web first is guided by the roller conveyor when it and thereby the dye is dried. During the drying and during the total fixing process the product web in view of the longitudinal tension is guaranteed to have a uniform fixing and thereby a uniform dye yield. A guidance of the product web by a roller conveyor moreover is a simple transporting method, when for example compared with a tension chain guidance, and makes possible simpler inlet and outlet in the treatment chamber.
An arrangement for continuous thermal treatment of a textile product web, in particular for dye treatment, comprises a steam-tight housing with at least one treatment chamber having a circulating device, i.e. a device for providing hot steam in a circulation process, at least one circulating fan, nozzle boxes arranged above and below the product web in each treatment chamber, a transporting device for a substantially flat or horizontal guidance of the product web through the housing, and at least one roller conveyor, as an essential part of the transporting device, arranged at a distance to the front wall of the housing. The distance to the front wall amounts to at least 20%, preferably 30%, of the length of the horizontal transporting path of the product web through the treatment chamber or chambers.
A rolling conveyor can have two rollers which are offset relative to one another. They are adjustable relative to one another by producing a longitudinal tension. A roller conveyor can have two rods or rollers which guide the product web in its transportation plane, and a pulling roller arranged between both rods or rollers above and below of the transporting plane and adjustable perpendicular to the transporting plane. In this case the product web is guided in form of the loop around the pulling roller and held by deviation of the pulling roller perpendicular to the transporting plane and the longitudinal tension. This device is especially suitable for the inventive method.
In the inventive device having at least two treatment chambers arranged one after the other, the roller conveyor is arranged in the region in which both treatment chambers abut against one another. In other words the distance of the roller conveyor to the front wall amounts to substantially 50% of the length of the horizontal transporting path of the product web through the treatment chambers. The treatment chambers are also called fields and the regions between the treatment chamber are also called field abutments.
The roller conveyor can have two guiding rollers and one vertically adjustable pulling roller. The guiding rollers are arranged closely one after the other and the pulling roller is arranged in the center under the guiding rollers. This arrangement of the guiding rollers and pulling rollers makes possible a small abutment region of the treatment chambers, or in other words the region of the regions in which no nozzle boxes are arranged.
The pulling roller can be formed simultaneously as an orienting roller. Therefore, additional means for orienting of the product web are dispensed with.
In accordance with a further feature of the present invention, the arrangement has locks before and after the housing. The locks extend from the bottom to above the transporting plane of the product web and have deviating rollers near the bottom end at the height of the transporting plane. The locks are subdivided into a lower, downwardly open pre-chamber and a further main chamber arranged over it. Suction passages or suction boxes can be connected with the pre-chambers. When compared with the known inlet and outlet slots with suction boxes disclosed in the German patent document DE-A 195 46 344, due to the separate locks with the pre-chamber and suction devices, the penetration of air and thereby condensation of steam to water is reliably prevented. A lock disclosed in the German patent document DE 198 58 839, in which steam is blown on the product web before the inlet slot of the housing, is less suitable for fixing of dye because of the danger of dye running.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.